1. Field of the Invention
This invention relates to the decomposition of formate esters and the purification of alcohols, such as tertiary butyl alcohol for use in the manufacture of methyl tertiary butyl ether. More particularly, this invention relates to a method for the substantially complete removal of formate impurities, including tertiary butyl formate, from tertiary butyl alcohol to be used in the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol.
Methyl tert-butyl ether is useful as a blending component in high octane gasoline.
2. Description of Related Art
Worrell U.S. Pat. No. 4,296,263 discloses the oxidation of isobutane with air to provide to tertiary butyl alcohol and tertiary butyl hydroperoxicle. It is disclosed that the reaction product, a solution of tertiary butyl hydroperoxide in tertiary butyl alcohol, contains minor amounts of oxygen-containing by-products such as acetic acid, formic acid and esters thereof that are purged from the system during purification of the reaction product.
The tertiary butyl hydroperoxide in the solution of tertiary butyl hydroperoxide in tertiary butyl alcohol can be decomposed thermally or catalytically to form additional tertiary butyl alcohol.
A number of catalysts have been proposed for this purpose, such as cobalt borate as disclosed in U.S. Pat. No. 4,547,598, a nickel, copper, chromia catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,704,482, an iron, copper, chromia, cobalt catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,705,903, a base treated hydrogenation catalyst from groups VIB or VIIIB of the Periodic Table as disclosed in Sanderson et al. U.S. Pat. No. 4,742,179, a nickel, copper, chromium and barium catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,873,380, a metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,910,349, an imidazole-promoted methyl metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,912,266, a base promoted metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,912,267, a solid ruthenium catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,922,033, a promoted metal porphine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,922,034, etc.
The tertiary butyl alcohol charge stock derived from tertiary butyl hydroperoxide in this manner will be contaminated with oxygen-containing impurities.
Processes for the manufacture of methyl tertiary butyl ether from tertiary butyl alcohol and methanol are known, as illustrated, for example, by Kruse et al. U.S. Pat. No. 5,243,091, Gupta U.S. Pat. No. 5,292,964, Hwan et al. U.S. Pat. No. 5,354,912, Kruse et al. U.S. Pat. No. 5,386,065, Kruse et al. U.S. Pat. No. 5,387,721 and Cassata et al. U.S. Pat. No. 5,395,982. In the practice of these processes, the tertiary butyl alcohol feedstock is passed through a peroxides decomposition reactor before being charged to an etherification reactor together with methanol for the formation of methyl tertiary butyl ether.
For example, Kruse et al. U.S. Pat. No. 5,243,091 discloses a method for the preparation of methyl tertiary butyl ether wherein the tertiary butyl alcohol is initially charged to a peroxides decomposition zone, which is typically a thermal decomposition zone. When the peroxides are to be thermally decomposed, the peroxides-contaminated tertiary butyl alcohol feedstock is conventionally passed through a peroxides decomposition reactor at a temperature of about 100.degree. C. to about 200.degree. C., a pressure of about 80 to about 500 psia at a flow rate of about 0.5 to 20 volumes of feedstock per reactor volume per hour to thereby provide a substantially peroxides-free tertiary butyl alcohol reaction product. The thus-treated tertiary butyl alcohol, which will still contain oxygen-containing impurities such as tertiary butyl formate, is then mixed with methanol and the mixture is catalytically reacted to form an etherification reaction product comprising unreacted methanol, unreacted tertiary butyl alcohol, water, isobutylene, methyl tertiary butyl ether, and oxygen-containing impurities present in the tertiary butyl alcohol feedstock. Methyl tertiary butyl ether is recovered from the reaction mixture.
Sanderson et al. U.S. Pat. No. 5,354,917 discloses a method wherein an isobutane oxidation product comprising a solution of 5 to 30 wt. % of tertiary butyl hydroperoxide in tertiary butyl alcohol is brought into contact with a catalyst consisting of alumina or carbon having rhodium deposited thereon in order to convert the tertiary butyl hydroperoxide to decomposition products, principally tertiary butyl alcohol. Sanderson et al. specify reaction conditions including a temperature of about 25.degree. C. to about 250.degree. C. and a pressure of about 0 to 1000 psig, with a temperature of about 40.degree. C. to about 150.degree. C. and a pressure of about 0 psig being preferred. Tertiary butyl alcohol is recovered from the decomposition products but will be contaminated with minor amounts of oxygen-containing impurities including peroxides and formites. As a consequence, if a tertiary butyl alcohol feedstock prepared by the Sanderson et al. process is to be used in the preparation of methyl tertiary butyl ether, the feedstock must be treated in a preliminary peroxides decomposition zone for the decomposition of the peroxide impurities.
A variety of other catalysts may be used to treat a tertiary butyl alcohol feedstock contaminated with peroxide impurities, such as cobalt borate as disclosed in U.S. Pat. No. 4,547,598, a nickel, copper, chromia catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,704,482, an iron, copper, chromia, cobalt catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,705,903, a base treated hydrogenation catalyst from groups VIB or VIIIB of the Periodic Table as disclosed in Sanderson et al. U.S. Pat. No. 4,742,179, a nickel, copper, chromium and barium catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,873,380, a metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,910,349, an imidazole-promoted methyl metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,912,266, a base promoted metal phthalocyanine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,912,267, a solid ruthenium catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,922,033, a promoted metal porphine catalyst as disclosed in Sanderson et al. U.S. Pat. No. 4,922,034, etc.